Reinforced ARP cylinder head studs Toyota 3UR-FE

The engine concerned

The 3UR-FE is Toyota's 5.7-litre petrol V8 (5,663 cc, bore 94 mm, stroke 102 mm), naturally aspirated with thirty-two valves, built since 2007; it powers the Toyota Land Cruiser 200, Sequoia and Tundra and the Lexus LX 570, among others. ARP devotes a single ARP2000 stud kit to it, the 203-4704, with 12-point nuts.

This V8 is originally fitted with head bolts, which these ARP studs replace.

Reinforced ARP cylinder head studs

Cylinder head fasteners work constantly: they hold the head tight against the block, crush the gasket to the right value and hold back the push of the gases at every combustion. If they lose even a little tension, the gasket starts to leak.

A single ARP kit is offered for this engine: the 203-4704, in ARP2000, with 12-point nuts, made for the cylinder heads of the 3UR-FE V8. ARP2000 is an ARP proprietary alloy, heat treated to reach 220,000 psi tensile strength, with threads rolled after heat treatment. Standard engine fasteners mostly belong to property classes 10.9 and 12.9 (150,800 to 176,900 psi minimum): ARP2000 therefore offers 24 to 46 % more margin. As an estimate, this ARP2000 kit, heat-treated to 220,000 psi tensile strength, is intended for tuned 5.7-litre V8 engines.

Technical specifications

Tightening torque

Technical guide

For assembly, ARP Ultra-Torque lubricant is used rather than engine oil. The tightening torque and tightening sequence are to be read in the instruction sheet supplied with the kit.

ARP undercut studs

On an undercut stud, ARP reduces the shank between the two threads. The studs then stretch more evenly from one to the next: the clamping force becomes more consistent and compensates for head gasket compression at installation, which reduces the risk of a blown gasket.

The ARP brand

Gary Holzapfel, a former aerospace engineer, created ARP (Automotive Racing Products) in the early 1970s to tackle engine failures caused by insufficiently strong fasteners in racing. Today the brand develops and manufactures thousands of parts in California, available in several material grades as needed.

Advantages over the original bolts

Criterion	Original head bolts	Reinforced ARP studs
Block threads	Stressed at every tightening	Less stressed: the stud stays in place

When studs become necessary

On an engine left standard, the original fasteners do their job. Switching to reinforced fasteners becomes worthwhile as soon as:

• 3UR-FE tuned, naturally aspirated or boosted: output beyond stock
• The compression ratio is increased
• A reinforced MLS gasket is fitted, with its need for a high and even preload
• The head has already lifted or the gasket has already failed
• The engine is used in competition, with intense heat cycles and repeated teardowns

Vehicle compatibility

Why is it the most cost-effective solution?

On a tuned 3UR-FE V8, the original head fasteners limit the pressure the gasket can take. ARP2000 studs with 12-point nuts push that limit higher, for a cost out of all proportion to an engine to be reopened after a failed gasket.